This invention relates to monitoring systems. More particularly, it relates to ventilator monitoring systems.
Ventilators are used to provide supplemental or complete respiration to a patient who is unable to maintain sufficient respiration without assistance. These ventilators provide positive pressure to force gas, e.g., air, into the lungs of a patient to assist in inspiration. This is followed by expiration by the patient without assistance. This cycle is repeated at a predetermined rate.
It is important that the effectiveness of supplemental or complete respiration be effectively determined. One method of accomplishing this is by periodic blood gas measurements. However, it is not feasible to monitor blood gas continuously. Therefore, the effectiveness of supplemental or complete respiration is monitored by measuring the volume of gas used to ventilate the patent.
Prior art monitoring systems monitor the output port of the expiration valve of the ventilator system. However, in actual practice under some conditions (i.e., simv*) the patient may not be required to take all of the gas delivered by the ventilator. Any excess gas from the ventilator is shunted into the expiration valve where it exits along with the gas volume expired by the patient. Thus, the expiration valve monitor may not monitor the true volume of gas expired by the patient but acturally a combination of patient gas and excess gas from the ventilator. FNT *synchronized intermittent mandatory ventilation.
It is therefore an object of this invention to provide an apparatus and method for monitoring only the gas volume actually expired by the patient in a ventilation system.